Yellow Light Emitting Device High Luminance
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Solution Overview
Problem
Current yellow light emitting devices, such as those using yellow LEDs or combinations of blue LEDs with fluorescent materials, struggle to produce high luminance yellow light with adjustable color tone and are limited by the need for high-density fluorescent material placement, which reduces light output due to blocking effects.
Innovation Solution
A light emitting device comprising a semiconductor light emitting element with a peak emission wavelength shorter than 490 nm, a fluorescent material for wavelength conversion, and a filter that cuts off mixing light, allowing transmission of light with specific chromaticity coordinates between dark green and yellowish red, thereby achieving high luminance and adjustable color tone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large amount of fluorescent material is disposed in very high density to obtain yellow light of desired color tone, then the color tone can be controlled, but the luminance becomes low due to light blocking by other particles
Solution Approach 1:
A resin layer is introduced as an intermediary medium between the blue LED and the yellow fluorescent material. This resin layer with optimized refractive index reduces light scattering and improves light extraction efficiency, allowing the fluorescent material to be distributed more uniformly without self-blocking, thereby maintaining high luminance while achieving desired color tone
Solution Approach 2:
The patent optimizes the refractive index parameter of the resin layer to match between the LED and fluorescent material, reducing optical impedance mismatch. This parameter change enables better light coupling and reduces the need for high fluorescent material density, solving the contradiction between color tone control and luminance maintenance
2Illumination intensity
If yellow color LED is used to emit yellow light, then the device is simple and compact, but the color tone cannot be adjusted and luminance is insufficient for signboard applications
Solution Approach 1:
The patent uses a blue LED combined with yellow fluorescent material that can serve multiple functions: the blue LED provides both direct blue light and excites the fluorescent material to produce yellow light. By adjusting the fluorescent material content and properties, the system can achieve different color tones (from yellow to white) while maintaining high luminance, making it universally applicable for various lighting requirements including signboards
3Duration of action of stationary object
If fluorescent lamp is used for signboard, then it is inexpensive and has high emission efficiency, but it has short life requiring frequent replacements and high running cost
Solution Approach 1:
The patent replaces the gas discharge mechanism of fluorescent lamps with a solid-state LED-based fluorescent conversion system. This substitution eliminates the mercury vapor and high-voltage discharge components that limit fluorescent lamp life, providing a more durable solid-state solution with longer service life and lower operating costs while maintaining high emission efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device emits light with high luminance and adjustable color tone from dark green to yellowish red, offering longer service life and improved design flexibility compared to traditional fluorescent lamps, while minimizing light blocking issues.
Implementation Method 1
a fluorescent material for wavelength conversion, which absorbs light from the light emitting element and emits light of a wavelength longer than that of the light from the light emitting element
Data Source
AI summary
An object of the present invention is to provide a light emitting device which emits light of deep yellowish color with high luminance. The light emitting device of the present invention comprises a light emitting element having a peak emission wavelength shorter than 490 nm, a fluorescent material for wavelength conversion which absorbs light from the light emitting element and emits light of a wavelength longer than that of the light from the light emitting element, and a filter which cuts off a part of a mixed light produced by mixing the light of the light emitting element and the light of the fluorescent material, wherein the light transmitted through the filter has a chromaticity coordinate on the chromaticity diagram according to CIE 1931 plotted in a region defined by a first point (x=0.450, y=0.450), a second point (x=0.250, y=0.650), a third point (x=0.350, y=0.750) and a fourth point (x=0.250, y=0.750) and in the region defined by a closed curve consisting of the monochromatic locus and the purple boundary.